1. Field of the Invention
The present invention relates to boilers having cyclonic combustion.
2. Description of the Related Art
In the past, cyclone combustors have been used to produce a cyclone of turbulent gases within a combustion chamber for combusting various solid materials, including poor quality coal and vegetable refuse. Such combustors are disclosed in "Combustion in Swirling Flows: A Review", N. Syred and J.M. Beer, Combustion and Flame, Volume 23, pages 143-201 (1974). A fluidized bed boiler having a cyclonic combustor is disclosed in U.S. Pat. No. 4,457,289 to Korenberg. These documents are incorporated by reference in this application. A fire tube boiler having a cyclonic combustor has been commercially marketed by Cyclotherm Division, Oswego Package Boiler Co., Inc.
Although providing high specific heat release, known adiabatic cyclone combustors have the disadvantages that combustion temperature is high and NO.sub.x emissions are high. Combustion is unstable at low capacity burning and high hydrodynamic turndown ratios are not possible in non-adiabatic combustors.
The hydrodynamic turndown ratio of the boiler is defined as the ratio of pressurized air flow at maximum load to pressurized air flow at minimum load and measures the ability of the boiler to operate over the extremes of its load ranges. A high turndown ratio would allow a wide range in the level of steam generation at a particular time. A wide range of steam generation is important to most efficiently allow the boiler to respond to varying steam demands.
It is an object of the present invention to provide a boiler utilizing cyclonic combustion and having a very high specific heat release, low excess air and a relatively low combustion temperature at low CO and NO.sub.x emissions.
It is also an object of the present invention to provide a boiler utilizing cyclonic combustion and which is stable at low capacity burning.
It is another object of the present invention to provide a boiler utilizing cyclonic combustion and having a high turndown ratio.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.